This invention relates to containers, tanks, and the like for storage of cryogenic liquids such as liquid natural gas (LNG), and is particularly concerned with containers and tanks of the above type formed of a concrete floor and unattached concrete wall, with foam or other insulation positioned around the inner surface of the container, including a corner structure which seals the container against liquid but allows for relative motion between the concrete wall and floor at the tank corner.
Many nations are now planning liquefied natural gas (LNG) energy importation projects. These projects require terminals which incorporate large cryogenic receiving tanks. Recent developments, including safety analyses for these tanks, have led designers to a double-tank arrangement where the outer tank will safely contain LNG in the event of an inner tank failure. This outer tank requires insulation between the inner and outer tanks, to protect the structure from thermal gradients and to minimize large quantities of gas that would evolve if the cold liquid were to contact the relatively warm outer tank wall.
Typically, the proposed outer tank design consists of a concrete floor slab with an unattached concrete wall. This wall will move radially relative to the floor for a variety of reasons, including dimensional changes due to concrete curing, external wall loads if an earthen berm is used, material shrinkage due to temperature effects of service and failure conditions, and hydrostatic loads due to liquid in the failed inner tank condition. Thus, an insulation system design is required which must seal against liquid and yet allow for relative motion between the outer tank wall and floor.
Applicant is not presently aware of any prior art insulation/seal design for a moveable concrete corner. Typically, this problem has been avoided by fixing the concrete wall to the floor. While simplifying the insulation and seal design, this fixity greatly magnifies the corner structural stresses, and results in a substantial increase in tank design complexity and cost.
An object of the present invention accordingly is the provision of a relatively simple outer tank corner structure, particularly for a cryogenic container formed of an outer concrete wall and concrete floor, and which provides structural thermal protection in the event of an inner tank failure. Another object is to provide a corner seal structure adjacent the inner surfaces of the concrete tank, which permits limited lateral movement of the bottom portion of the concrete wall with respect to the floor, under service conditions, without undue stresses.